Two-Level Cervical Disc Replacement vs Two-Level ACDF

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Abstract and Introduction
Methods
Results
Discussion
Conclusion
References
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Abstract and Introduction

Abstract

Study Design: Retrospective cohort study.

Objective: The aim of this study was to evaluate the safety of two-level cervical disc replacement (CDR) in the outpatient setting.

Summary of Background Data: Despite growing interest in CDR, limited data exist evaluating the safety of two-level CDR in the outpatient setting.

Methods: The National Surgical Quality Improvement Program (NSQIP) database was queried for all two-level anterior cervical discectomy and fusion (ACDF) and CDR procedures between 2015 and 2018. Demographics, comorbidities, and 30-day postoperative complication rates of outpatient two-level CDR were compared to those of inpatient two-level CDR and outpatient two-level ACDF. Radiographic data are not available in the NSQIP.

Results: A total of 403 outpatient CDRs were compared to 408 inpatient CDRs and 4134 outpatient ACDFs. Outpatient CDR patients were older and more likely to have pulmonary comorbidities compared to inpatient CDR (P < 0.03). Outpatient CDR patients were less likely to have an American Society of Anesthesiologists class ≥2 and have hypertension compared to outpatient ACDF patients (P < 0.0001). Outpatient CDR had a lower 30-day readmission rate (0.5% vs. 2.5%, P = 0.02) and lower 30-day reoperation rate (0% vs. 1%, P = 0.047) compared to inpatient CDR. Outpatient CDR had a lower readmission rate (0.5% vs. 2.1%, P = 0.03) compared to outpatient ACDF, but there was no difference in reoperation rates between the two procedures (0% vs. 0.8%, P = 0.07). Outpatient CDR had an overall complication rate of 0.2%, inpatient CDR had a complication rate of 0.9%, and outpatient ACDF had a complication rate of 1.3%. These differences were not significant.

Conclusion: To our knowledge, this is the largest multicenter study examining the safety of two-level outpatient CDR procedures. Outpatient two-level CDR was associated with similarly safe outcomes when compared to inpatient two-level CDR and outpatient two-level ACDF. This suggests that two-level CDR can be performed safely in the outpatient setting.

Level of Evidence: 3

Introduction

In the United States, cervical disc replacement (CDR) has grown in popularity over the past decade. From 2009 to 2015, CDR increased in utilization at a rate of 17% per year without any evidence of plateauing.^[2] As the population continues to age, the demand for cervical spine surgery, including CDR, will continue to increase as the incidence of symptomatic cervical spine disease continues to rise.^[37]

Anterior cervical discectomy and fusion (ACDF) and CDR provide a means for effective discectomy, restoration of disc space height, and decompression of spinal stenosis.^[1,2] Many studies, including several meta analyses, have shown that both procedures have similarly good outcomes for the treatment of degenerative cervical disc disease.^[3–8] Research also shows that single and multilevel CDR procedures are safe compared to ACDF.^[3,5,9] One advantage of CDR is the potential for preserved range of motion in the long term.^[10] This preservation of motion could theoretically reduce the intradiscal pressure at adjacent levels thereby lowering the incidence of adjacent segment disease, a common complication that affects up to 25.6% of ACDF patients within 10 years.^[28] Koreckij et al^[29] suggest that there is evidence showing lower rates of revision surgery due to adjacent segment disease in patients treated with CDR compared to ACDF, particularly in two-level procedures.

As the volume of spine surgeries continues to grow, many procedures are now performed in an outpatient setting. This trend can be attributed to the decreasing invasiveness of surgery, patients' desire to spend less time in the hospital, and significant cost benefits. These factors all contribute to increased value-based care.^[11] The progressive transition toward ambulatory care has fostered significant research interest in the comparison of clinical outcomes and safety profiles between outpatient and inpatient procedures.^[11] Several studies have found outpatient one- two-level ACDF to be safe, with low complication rates comparable to inpatient ACDF.^[32–35] Recently, outpatient single-level CDR has also been found to yield similarly good outcomes compared to inpatient single-level CDR.^[26]

Despite the growing trend of performing CDR in the outpatient setting,^[2] to our knowledge, no previous study has compared the safety of outpatient two-level CDR to two-level ACDF on a large scale. Furthermore, beyond the published Food and Drug Administration (FDA) Investigational Device Exemption (IDE) studies,^[31,36] the current evidence regarding the safety of outpatient two-level CDR is limited. Therefore, the purpose of this study is to analyze the safety of outpatient two-level CDR compared to inpatient two-level CDR and outpatient two-level ACDF through a national, multicenter database.

Table 1. Distribution of Procedures by Year Performed
	Outpatient CDR	Inpatient CDR*	Outpatient ACDF
2015	28 (7.0%)	52 (12.8%)	727 (17.6%)
2016	51 (12.7%)	95 (23.3%)	895 (21.7%)
2017	130 (32.3%)	145 (35.5%)	1233 (29.8%)
2018	194 (48.1%)	116 (28.4%)	1279 (30.9%)
Total	403	4134	408

ACDF indicates anterior cervical discectomy and fusion; CDR, cervical disc replacement.
*Cochran-Armitage Trend Test yielded a statistically significant increase in the proportion of outpatient CDR procedures compared to inpatient CDR procedures over the study period (P < 0.0001).

Table 2. Patient Demographic and Preoperative Comorbidities
Characteristics	Outpatient CDR	Inpatient CDR		Outpatient ACDF
Characteristics	N = 403	N = 408	P	N = 4134	P
Sex			0.47		0.048*
Male	217 (53.8%)	209 (51.2%)		2012 (48.7%)
Female	186 (46.2%)	199 (48.8%)		2122 (51.3%)
Age y	49.3 ± 9.9	47.7 ± 10.9	0.03*	54.8 ± 10.2	<0.0001*
BMI, kg/m²	30.1 ± 6.7	29.7 ± 6.5	0.4	30.7 ± 6.4	0.06
ASA			0.8		<0.0001*
ASA 1–2	293 (72.7%)	300 (73.5%)		2428 (58.7%)
ASA >2	110 (27.3%)	108 (26.5%)		1705 (41.3%)
Diabetes	52 (12.9%)	45 (11.0%)	0.4	583 (14.1%)	0.5
Smoke	92 (22.8%)	90 (22.1%)	0.8	1126 (27.2%)	0.06
Dyspnea	18 (4.5%)	3 (0.7%)	0.0008*	238 (5.8%)	0.3
History of COPD	13 (3.2%)	4 (1.0%)	0.03*	167 (4.0%)	0.4
Hypertension	114 (28.3%)	126 (30.9%)	0.4	1871 (45.3%)	<0.0001*
Wound infection	1 (0.2%)	0 (0%)	0.3	5 (0.1%)	0.5
Steroid use	8 (2.0%)	8 (2.0%)	0.98	126 (3.0%)	0.2
Bleeding disorder	6 (1.5%)	3 (0.7%)	0.3	38 (0.9%)	0.3
Sepsis	2 (0.5%)	3 (0.7%)	0.7	6 (0.1%)	0.1

ACDF indicates anterior cervical discectomy and fusion; ASA, American Society of Anesthesiologists; BMI, body mass index; CDR, cervical disc replacement; COPD, chronic obstructive pulmonary disease.
*Indicates statistical significance; P values represent comparison between outpatient CDR and the respective cohort.

Table 3. Operative Time, Length of Stay, Readmissions, and Reoperation Rates
	Outpatient CDR	Inpatient CDR	P	Outpatient ACDF	P
Operative time, h	123.4 ± 49.3	143.7 ± 45.5	< 0.0001*	119.5 ± 54.2	0.13
Length of stay, days	0.68 ± 2.66	1.61 ± 5.4	< 0.0001*	0.98 ± 1.5	0.06
30-day Readmission	2 (0.5%)	10 (2.5%)	0.02*	88 (2.1%)	0.03*
30-day Reoperation	0 (0%)	4 (1%)	0.047*	33 (0.8%)	0.07

ACDF indicates anterior cervical discectomy and fusion; CDR, cervical disc replacement.
*Indicates statistical significance.

Table 4. Postoperative Complications
	Outpatient CDR	Inpatient CDR	P	Outpatient ACDF	P
Major Complications: life-threatening	0 (0%)	2 (0.5%)	0.2	25 (0.6%)	0.12
Sepsis	0 (0%)	0 (0%)		3 (0.1%)	0.6
Septic shock	0 (0%)	0 (0%)		1 (< 0.1%)	0.8
Acute renal failure	0 (0%)	0 (0%)		0 (0%)
Pulmonary embolism	0 (0%)	0 (0%)		6 (0.1%)	0.4
Ventilator >48 h	0 (0%)	0 (0%)		3 (0.1%)	0.6
Unplanned intubation	0 (0%)	1 (0.2%)	0.3	7 (0.2%)	0.4
Myocardial infarction	0 (0%)	0 (0%)		3 (0.1%)	0.6
Cardiac arrest requiring CPR	0 (0%)	0 (0%)		2 (< 0.1%)	0.7
Stroke with neurological deficit	0 (0%)	1 (0.2%)	0.3	0 (0%)
Minor Complications: not life-threatening	1 (0.2%)	2 (0.5%)	0.6	32 (0.8%)	0.2
Urinary tract infection	1 (0.2%)	0 (0%)	0.3	5 (0.1%)	0.5
Pneumonia	0 (0%)	1 (0.2%)	0.3	9 (0.2%)	0.3
Superficial SSI	0 (0%)	0 (0%)		7 (0.2%)	0.4
Deep SSI	0 (0%)	0 (0%)		4 (0.1%)	0.5
Organ/space SSI	0 (0%)	0 (0%)		4 (0.1%)	0.5
Wound dehiscence	0 (0%)	1 (0.2%)	0.3	0 (0%)
DVT requiring therapy	0 (0%)	0 (0%)		3 (0.1%)	0.6
Overall complications	1 (0.2%)	4 (0.9%)	0.2	57 (1.4%)	0.054

ACDF indicates anterior cervical discectomy and fusion; CDR, cervical disc replacement; CPR, cardiopulmonary resuscitation; DVT, deep vein thrombosis; SSI, surgical site infection

Table 5. Multivariate Regression Analysis
	Readmissions (OR With P)	Reoperations (OR With P)	Overall Complications (OR With P)
Procedure
Outpatient CDR	Ref	Ref	Ref
Inpatient CDR	5.69 (1.23–26.26); P = 0.026*	N/A	6.29 (0.75–52.76); P = 0.09
Outpatient ACDF	3.39 (0.83–13.92); P = 0.09	N/A	3.40 (0.46–24.94); P = 0.23
Other preoperative factors
Sex (male)	1.11 (0.74–1.66); P = 0.61	1.16 (0.60–2.22); P = 0.66	0.68 (0.39–1.20); P = 0.18
Age (per unit)	1.03 (1.01–1.05); P = 0.0035*	1.01 (0.97–1.04); P = 0.67	1.01 (0.98–1.04); P = 0.37
Dyspnea	1.66 (0.86–3.23); P = 0.13	0.77 (0.17–3.37); P = 0.73	1.75 (0.71–4.31); P = 0.22
COPD	1.79 (0.87–3.66); P = 0.11	1.16 (0.26–5.11); P = 0.85	0.53 (0.12–2.30); P = 0.40
Hypertension	1.08 (0.70–1.67); P = 0.73	1.07 (0.52–2.18); P = 0.86	0.98 (0.53–1.78); P = 0.94
ASA >2	1.92 (1.22–3.01); P = 0.0047*	1.92 (0.94–3.93); P = 0.07	3.31 (1.74–6.31); P = 0.0003*

*indicates statistical significance
ACDF indicates anterior cervical discectomy and fusion; ASA, American Society of Anesthesiologists; COPD, chronic obstructive pulmonary disease; OR, odds ratio; Ref, reference value for other procedures.

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Comparison of Two-Level Cervical Disc Replacement Versus Two-Level Anterior Cervical Discectomy and Fusion in the Outpatient Setting

Abstract and Introduction

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